Another Cable Thread

[oldtimer]

In my search for cheap interconnects, specifically balanced xlr, I have run across those that are called "audio cables" and also "digital transfer cables." Audio cables for example might have 22 awg twisted copper wire with aluminum shielding and digital transfer would have 110 ohm belden cable. Is there any benefit for the home environment to either? These are to be used with a sunfire prepro to sunfire amp for both 2 channel and ht applications. any thoughts?

[Guest " "]

Are you talking about using a AES/EBU XLR cable

[oldtimer]

Thanks Fritz the belden 110 ohm cable is labled as AES/EBU, others which use different cable or wire do not have the designation. There is obviously a difference in construction, is there a difference in suitability and therefore desirability for the application?

[Guest " "]

AES/EBU is a balanced coax standard for digital connections. I would not say that AES/BEU is a better cable than an analog XLR.

If your connecting an analog driver stage connection to a power amp, I would stick with analog XLR cables. I use Monster M-1000, M-2000, M-2000 Sigma, and SP-1000 only because I sometimes get them used cheap. The SP-1000 is a stepped up commercial grade for commercial gear. M-1000 is the top of the line for the average consumer market. M-2000 and M-2000 sigma is an upscale line.

There are other brands.

[Islander]

On a related topic, are digital coax cables any better than regular interconnects? Since regular analog interconnects are supposedly unable to carry digital info properly, do the different features/construction of digital coax cables also make them better able to carry analog signals?

I'm asking because they're not much more expensive than some analog RCA-to-RCA interconnects, and much less expensive than higher-end analog interconnects.

[oldbuckster]

www.monoprice.com ................ take a look here, some other forum member posted this .............. good prices

[DrWho]

Since regular analog interconnects are supposedly unable to carry digital info properly

I have never had any problems using "analog" interconnects for my "digital" signals. Although the data is digital, the actual voltages representing the data are still analog. It's really no different than sending any other analog signal.

[oldtimer]

has anyone bought male to female xlr cables from monoprice? All I see on their product list are rca to xlr's.

[Guest " "]

"I'm asking because they're not much more expensive than some analog RCA-to-RCA interconnects, and much less expensive than higher-end analog interconnects."

ummm....more factors...before thinking about going XLR...you need to determine what type of XLR architecture you have. your manuals, schematics, online reviews, etc can help figure this out...if nothing else you can always ask the manufacture.

So before we get into this the basic layout is Pin 1 = shield (ground) Pin 2 = White or Red (+ or "hot") Pin 3 = Black (-)

Note that pin 2 is the upper half of the sine wave and pin 3 is the lower half...this means that the signals are inverted

In the ideal state...your pre-amp out and amp in XLR circuts will use seperate amplifiers to process the split signals

In more common senerio's, a transformer is used to convert a normal full phase (upper and lower sine wave) signal into a balanced split one. This is done by basically changing the ground reference using the transformer. In even cheaper senerios...resistors are used to change the ground reference.

A under handed approach to implement XLR is to simply connect a normal full sine wave signal to pin 2. This gives you an xlr connector but not a balanced one.

so, if you have a fully balanced XLR architecture that used split signals that are seperately processed than I would recommend going for XLR cables.

If your system uses transformers, I would consider it only if the runs are long.

if your system uses the underhanded method...I would not bother.

Bottom line....it's not the cable that brings value to an xlr capable system...it's the actual architecture in use.

[DrWho]

Note that pin 2 is the upper half of the sine wave and pin 3 is the lower half...this means that the signals are inverted



In the ideal state...

That's not true, nor is the notion of pin 3 carrying an opposite phase signal. The only thing a balanced connection provides is an equal output impedance and an equal input impedance so that common mode noise has equal amplitude on both legs and then gets rejected with the differential input. The reason for the 6dB gain is because the input voltage is not being referenced to ground.

An engineer that doesn't understand common mode rejection could certainly put an inverted output stage on pin 3 and everything can work. However, it is not guaranteed to work. If the output stages don't have the same output impedance, then the common mode rejection no longer works.

In other words, one can absolutely send the signal only over pin 2 and achieve the common mode rejection (in many cases it achieves better CMR). The only purpose that balanced connections serve is to provide noise immunity. If noise is not an issue, then there is good argument that an unbalanced connection should actually yield better performance.

Shame on me for not providing any references to more reliable sources. If anyone wants to research this further, let me know, and I can provide all sorts of documentation. Personally, I find the technical details very fascinating, but I understand not everyone is interested.

With that in mind, if you're trying to optimize the performance of your balanced interconnects, then the best thing you can do is ensure that the line impedance seen on pins 2 and 3 is near identical as possible, which means using high tolerances for the copper and guage of wire being used. It also doesn't hurt to use twisted pair wire surrounding by a braided shield, which will reduce the amount of potential noise picked up and thus reduce the amount of common mode rejection required by the line. I would like to note, however, that this is way way over-engineering the solution. There is no advantage to increasing the signal-to-noise ratio of the electronics when the noise floor of the playback environment is many orders of magnitude larger.

[Guest " "]

I indicate 3 types of xlr implmentation and explained each.

Your saying that an implementation using inverted signals is "not true", I guess I better go turn off my pre-amp,

[Guest " "]

Like I said...there are 3 types of XLR implementation that I know of...and yes...one use a split phasing approach.

[Guest " "]

Here is the pin break out....2 is positive, 3 is inverted

[PrestonTom]

"....

I indicate 3 types of xlr implmentation and explained each. Your saying that an implementation using inverted signals is "not true", I guess I better go turn off my pre-amp

...."

What Dr Who was responding to was your use of the phrases that suggested one pin was carrying the upper half of the signal (+) and the other pin was carrying the lower half (-). That would certainly be confusing to others. Obviously both pins are carrying the same signal, albeit the one is 180 deg out of phase.

So it is probably safe to turn your pre-amp back on.

-Tom

[DrWho]

You missed the purpose of my post...the only advantage to balanced connections is their noise rejection. The noise rejection works when the output impedance of both legs are the same. What the signal does is completely irrelevant. Heck, why not present an implementation that sends the signal over the ground conductor? It just leads to more confusion and has no bearing on what the circuit is trying to achieve.

The accepted AES standard is to send the signal only on pin 2. Granted, the standard has not always been in existence, but it has been adopoted due to the problems that have crept up.

Implementations that deviate from the standard are just that....deviations - and absolutely should be addressed individually. However, in the case of the actual interconnect itself, the deviations have absolutely no influence on what constitutes a good interconnect. Why's that? Because the circuits in question exist only for the purpose of transferring a signal without introducing noise - which is a function of the impedances, NOT what the signal is doing.

[DrWho]

What Dr Who was responding to was your use of the phrases that suggested one pin was carrying the upper half of the signal (+) and the other pin was carrying the lower half (-). That would certainly be confusing to others. Obviously both pins are carrying the same signal, albeit the one is 180 deg out of phase.

Thanks Tom, that's exactly what I was referring to. What's crazy is that implementation would actually work [] (talk about crossover distortion though)

[Islander]

www.monoprice.com ................ take a look here, some other forum member posted this .............. good prices

Very good prices, but are they any better quality than what you'd find at Radio Shack or The Source by Circuit City?

[oldtimer]

Pat, I repeat my question, did you see any m/f xlr cables on their site? I could not, only rca to xlr.

[Islander]

"I'm asking because they're not much more expensive than some analog RCA-to-RCA interconnects, and much less expensive than higher-end analog interconnects." ummm....more factors...before thinking about going XLR...you need to determine what type of XLR architecture you have.

Thanks for the info, fritz, but I was asking about non-XLR cables. That's why I called it a related topic. What's your opinion on "digital" RCA-to-RCA interconnects compared with regular "analog" ones? Dr Who sees no benefit. Could it be yet another marketing scam?

We were told the same thing in the photography field with digital flash units. Supposedly, the old school $15 cables couldn't carry the "high-speed" digital info clearly enough for the new flashes to communicate properly with the cameras. Naturally, the new digital cables cost $100...

Sorry to ignore you, oldtimer, we were both typing at the same time.

[Guest " "]

""Thanks for the info, fritz, but I was asking about non-XLR cables. That's why I called it a related topic. What's your opinion on "digital" RCA-to-RCA interconnects compared with regular "analog" ones? Dr Who sees no benefit. Could it be yet another marketing scam?"""

In digital coax applications, I've come across situations where the digital signal would not carry on a regular RCA cable but would carry on a "digital" coax rca cable.

So now...if at one point we were asking about using "digital" coax rca cable as an improved RCA line level cable, I don't think it will turn out to be.